With reference initially to FIGS. 1, 2A, and 2B, there follows a description of the essential members of a prior art type of bending press.
As can be seen in FIG. 1, the bending press comprises a stationary bottom panel 12, a vertical frame 14, and a moving top panel 16 capable of moving vertically relative to the stationary bottom panel 12. The top panel 16 is moved by means of two control actuators 18 and 20.
The stationary bottom panel 12 has bending dies such as 22 fixed thereon, the right section of a die perpendicular to the plane of the figure being V-shaped. The moving top panel 16 serves to carry bending tools or punches 24. Each punch 24 is fixed to the top panel 16 by being clamped between a stationary or intermediate piece 26 which is releasably fixed to the top panel 16, and a pivoting clamp 28 mounted on the intermediate piece 26. Each clamp 28 can pivot relative to the associated intermediate piece 26 about an axis XX′ common to all of the intermediate pieces and parallel to the long direction of the bending press.
With reference to FIGS. 2A and 2B, there follows a more detailed description of how the punches 24 are fixed. Each clamp 28 comprises a middle portion 28a which receives a pivot axis extending parallel to the long direction of the top panel and which is constituted in this particular example by hemispherically-headed screws 30 engaged in the intermediate piece 26. Each clamp 28 also has a control top end 28b and a clamping bottom end 28c. The tang 32 of the punch 24 has two clamping faces 32a and 32b for pressing respectively against the clamping surface 34 of the intermediate piece 26 and the clamping surface 35 at the bottom end 28c of the clamp 28. Pivoting of the clamp about the axis defined by the heads of the screws 30 is controlled by pushers 36 each having one end 36a co-operating with the end 38b of the clamp and having a second end 36b co-operating with a pivot-controlling cam 38. It will be understood that by acting on the control cam 38, the pushers 36 are caused to move so as to cause the end 28c of the clamp 28 to go from the clamping position shown in FIG. 2A to the release position shown in FIG. 2B. In this second position, the tool 24 can be removed from the top panel 16.
Mechanical systems other than the pivoting cam 38 could be used for controlling pivoting of the clamp 28. In general, two major types of clamp control can be provided, either control associated with each clamp mounted on an intermediate piece, or else overall control for all of the clamps on the intermediate pieces mounted on the entire top panel 16.
When the bending operations to be performed with the press need to be modified, it is necessary to begin by replacing the tools or punches that were previously mounted on the top panel with new punches. As a general rule, these changes apply to only a fraction of the tools, and thus to only a fraction of the intermediate pieces and clamps 28 of the top panel. In addition, it will be understood that these tool-changing operations and the adjustments that need to be performed after changing a tool constitute periods during which the bending press is not in use. It is therefore very useful to have bending presses in which these stages, in particular tool-changing stages, can be implemented using a minimum number of operations leading to the machine being out of action for a minimum length of time.